Microbial culturing experiments at high pressures have implications in food science, virus-related research and studies involved in the development of energy resources. Because oxygen solubility is increased at high pressure, the occurrence of large dissolved oxygen tension induces biological oxidative stresses that can affect the function of biological membranes, the physical/-chemical properties of enzymes and regulate virulence and toxin production in pathogens (Follonier et al., Pressure to kill or pressure to boost: a review on the various effects and applications of hydrostatic pressure in bacterial biotechnology, Appl. Microbiol. Biotechnol., 93: 1805-1815, 2012, and references cited therein). Therefore, the food industry has been developing protocols to inactivate microorganisms by applying pressure stresses without the use of temperature treatment that alters food properties (Id.). That pathogens become inactive under high hydrostatic pressure while maintaining intact the interactions and structures required to induce immune responses also makes high pressure microbial studies relevant for the development of high-pressure vaccines (Id.). Future studies on the antibiotic resistance of gram-negative bacteria may be linked to high pressure incubations of extremophile organisms similar to those thriving in the deep ocean (e.g. Alain et al., Marinitoga piezophila sp. nov., a rod-shaped, thermo-piezophilic bacterium isolated under high hydrostatic pressure from a deep-sea hydrothermal vent., Int. J. Syst. Evol. Microbiol. 52: 1331-1339 (2002); Takai et al., Thiomicrospira thermophilia sp. nov., a novel microaerobic, thermotolerant, sulfur-oxidizing chemolithomixotroph isolated from a deep-sea hydrothermal fumarole in the TOTO caldera, Mariana Arc, Western Pacific. Int. J. Syst. Evol. Microbiol. 54: 2325-2333 (2004)). High pressure microbial studies are also focused on the development of high-pressure vaccines.
High pressure continuous culturing approaches can also affect our understanding of microbial processes associated with petroleum biodegradation and evolution deep in the Earth's subsurface. Recent studies have reported the microbial formation of diesel-like hydrocarbons by Escherichia coli strains (Choi et al., Microbial production of short-chain alkanes, Nature, 502, 571-574, 2013). Native microbial populations in petroleum reservoirs include a wide range of anaerobic bacteria and archaea that are commonly found in deep-sea hydrothermal vents (e.g. Head et al., biological activity in the deep subsurface and the origin of heavy oil, Nature, 426, 344-352. (2003). Thermococcus, Archaeoglobus, and Thermotoga) (Head et al. 2003). Bacteria capable of petroleum biodegration or synthesis at in-situ high pressure and temperature, however, have not been isolated yet. Moreover, there are many other challenges in the area of high pressure microorganisms that could be overcome with development of the proper culturing and sampling systems. One such challenge may be overcome by the future integration of sampling petroleum systems with laboratory incubations at in-situ pressures.
For at least the above reasons, there is a need to provide systems and methods to study the rates of microbially-mediated petroleum degradation and the efficiency of aerobic microorganisms for biofuel synthesis at pressure and temperature conditions resembling those of the Earth's interior. More broadly, there is a need to provide systems and methods to study different types of microorganisms under high pressure and, in some circumstances, high temperature conditions while permitting periodic, non-damaging sampling of the incubated organisms.